Obtaining real-time 3D co-ordinates of a moving object has many applications such as gaming [1], robotics and human-computer interaction applications [2-4], industrial applications etc. Various technologies have been investigated for and used in these applications, including sensing via wire-interfaces [2], ultrasound, and laser interferometry. However a simple and low cost solution that can provide enough precision and flexibility has not been available. Recent proliferation of low-cost inertial sensors has not addressed the problem of position tracking. Cassinelli et al demonstrated a scanning mirror-based tracking solution [3-4]; however their system does not solve the problem of object searching/selecting and does not have adequate depth (Z-axis) measurements.
In addition it is often desirable to obtain good resolution on the position of the object when it is close to the tracking system. Unfortunately, many existing tracking systems tend to lose resolution when the object is close in.
Many video-based tracking systems utilize charge-coupled device (CCD) arrays to obtain position information from an image of the object that is being tracked. Unfortunately, the image is two-dimensional and additional information is usually needed in order to derive three-dimensional position information. In addition, a CCD typically has a limited field of view. Furthermore, there is a large cost differential associated with increasing the resolution of CCD array.
Another technology is barcode scanning which uses a scanning mirror, a light source and a photo sensor to receive the varying reflected back light source from the barcode to extrapolate varying voltages and further information from there. This type of system requires the barcode to be stationary as it is being scanned. Similarly, other scanning technologies such as flatbed scanners use the setup of measuring the voltage from a photo sensor of the amount of light that is scanned and reflected back from an object that is stationary. The restriction in this case is the same as above with CCD sensors, which is the scan is in two dimensions.
In any such imaging, tracking, or position measurement applications which incorporate optical beam scanning and receiving of light by a photosensor, it would be desirable to utilize the miniature size and low-power scanning capability of MEMS mirrors. The small size of the scanning unit could result in lower cost, faster scanning, and portable implementations, but it creates a problem for the system designer in that the small mirror aperture receives a very tiny portion of the reflected light, perhaps too low for most applications. Therefore it is of interest to decouple the design of the scanning/mirror unit (keep it very small,) and the receiving or photosensing unit (keep it as large as necessary to receive enough optical power.)
It is within this context that embodiments of the present invention arise.